GPencil: Convert and Bake mesh animation to grease pencil strokes

This patch adds two options:

- Convert a mesh to grease pencil strokes.
- Bake the mesh animation into grease pencil strokes.

Both are related and must be included in the same patch.

Related to tasks: T77629 and T77630

Notice: The conversion is done for mesh edges and it's not considering any visibility clipping. All edges are exported, no matters if it's visible or not.

Example of Convert a Mesh to Grease Pencil strokes:

{F8606028}

This conversion was inspired by the technique used by @luamono in this tweet: https://twitter.com/luamono/status/1239983662176841730

Example of Bake Animation (the video is a little outdate, but the basic functionality is the same, only small changes in UI):

{F8606032}

Reviewed By: mendio, pepeland

Maniphest Tasks: T77629, T77630

Differential Revision: https://developer.blender.org/D7983

1 files changed, 13 insertions, 0 deletions

diff --git a/source/blender/blenkernel/BKE_gpencil_geom.h b/source/blender/blenkernel/BKE_gpencil_geom.h
index b26016aa26c..b79bbf3948f 100644
--- a/source/blender/blenkernel/BKE_gpencil_geom.h
+++ b/source/blender/blenkernel/BKE_gpencil_geom.h
@@ -98,6 +98,19 @@ bool BKE_gpencil_stroke_shrink(struct bGPDstroke *gps, const float dist);
 
 float BKE_gpencil_stroke_length(const struct bGPDstroke *gps, bool use_3d);
 
+void BKE_gpencil_convert_mesh(struct Main *bmain,
+                              struct Depsgraph *depsgraph,
+                              struct Scene *scene,
+                              struct Object *ob_gp,
+                              struct Object *ob_mesh,
+                              const float angle,
+                              const int thickness,
+                              const float offset,
+                              const float matrix[4][4],
+                              const int frame_offset,
+                              const bool use_seams,
+                              const bool use_faces);
+
 #ifdef __cplusplus
 }
 #endif